1. Field of the Invention
The present invention relates to a plastic wrap with a cling layer. More specifically, the present invention relates to a plastic wrap having an adhesive cling layer wherein the adhesive layer is modified to reduce or eliminate the amount of cling produced until the modified surface is disrupted by stretching/application of the wrap.
2. Description of the Related Art
Olefinic polymers, particularly polymers of ethylene, are employed in a variety of end use applications including the preparation of wrapping films. In conventional wrapping processes, e.g. spin or rotary stretch wrapping techniques, the polymeric film is wound under tension around a package by either rotating the package on a turntable or by winding the film around a stationary package. In such applications, it is generally desirable for the overlapping portions of the film to adhere to each other thereby self-sealing the wrap without the need for an external adhesive or heat sealing operation.
To achieve the above, it has been proposed to provide one surface of the wrap with cling properties which allow the wrap to cling to itself, and to provide the other side with so called "slip" characteristics which endow a low coefficient of friction on an outer, non-cling surface. The provision of this slip surface prevents adjacent packages which are wrapped individually in cling wrap, from sticking to each other and from undergoing possible damage when pulled apart.
In order to impart cling properties or improve the cling of the cling side of such films, it has been proposed to add tackifying additives or to use acrylates in the (co)polymer. However, the use of tackifiers has disadvantages in that, while these enhance the cling properties of the wrap they tend to induce a number of drawbacks. For example, they tend to have an adverse effect on the optical properties of the film and enhance surface migration of the additive(s). This type of migration can induce rolls of the wrap to telescope and/or collapse. A further problem is encountered in the instance wherein the tackifier is "picked off" onto the slip side of the film while the film is rolled due to the slip and cling layers being maintained in intimate contact.
In order to promote the slip characteristics of the slip surface of the wrap, it is possible to treat one side (viz., the outer, non-cling side) of the film in a manner which promotes a reduction in the coefficient of friction. This can be achieved through the use of anti-cling and/or antiblock additives including silicas, silicates, diatomaceous earth and various lubricants. U.S. Pat. No. 5,225,257 to Brant discloses the use of corona discharge for modifying the outer slip surface of the wrap and for improving the anti-cling characteristics.
However, despite the above progress, a drawback is encountered in that the very cling characteristics which are vital during application, tend to interfere with handling and storage during production, roll release and ease of use by the consumer.
Accordingly, there still exists a need for a plastic cling wrap which is easy to handle during production and storage, and which still produces the desired amount of "cling" when used to wrap an article or the like.